Copper oxide rectifier



Feb. 9, 1932. J. SLEPIAN 1,844,928

I COPPER OXIDE RECTIFIER Filed Sept. 30, 1921 INVENTOR J05 6,0/2 J/6P/C7/7 ATTORNWEY Patented Feb. 9, 1932 UNITED STATES PATENT OFFICE JOSEPH BLEPIAN, OI PITTSBURGH, PENNSYLVANIA, ASSIGNOB TO WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION 01' PENNSYLVANIA COPPER OXIDE RECTIFIER Application fled September 80, 1927. Serial 110.223.019.

surfaces of electrode materials.

One object of my invention is to provide means by which an electrolytic process may be racticed at the surface of a material wit out subjecting it to too intimate or too 1 prolonged contact with the electrolyte.

Another object of my invention is to provide means for electrolytically affecting the surface of a porous material without permitting an appreciable impregnation of the material by the electrol te.

A further object o my invention is to provide means by which the surface of an oxidized copper electrode may be reduced by electrolysis without permittlng the electrode to become saturated with the electrolyte.

Other objects of my invention will become evident through reading the following specification, taken in connection with the drawin s wherein:

igure 1 is a dia rammatic side elevation of an apparatus em odying one form of my invention, and

Fig. 2 is a diagrammatic representation of another embodiment thereof.

In connection with the manufacture of oxidized copper blanks to be assembled into rectifiers of the thin-layer type, it has been desirable to reduce the outer surface of an oxidized layer by making it the negative electrode in an electrolytic cell containing dilute acid or other electrolyte. Such an oxidized surface is very likely to contain numerous cracks and pores, and difficulty arises from the fact that the electrolyte may penetrate these pores and thereb make contact with the mother copper eneath the oxide layer. This results in an increase of the inverse current through the resulting rectifier units and is undesirable.

In accordance with my invention, the above-mentioned diflicult is avoided by subjecting the oxidized sur aces to electrolytic action, not by immersing them in a liquid electrolyte, as is the common process in the electrolytic art generally, but by placing them in contact with a pad of asbestos, or other 'chemically inert fibrous material, which is impregnated to a rcater or less degree, by the electrolyte. 5y this means, the oxide surface never comes in contact with any large amount ofyfree liquid, and it has been found that the penetration of liquid through the oxide layer is practically avoided. Referring particularly to Fig. 1, a blank of copper 1, having a surface layer 2 of oxide thereon, is connected to the negative terminal 3 of a source of current 4. Upon the layer 2 is laid a pad 5 which may be of woven asbestos partially saturated with an electrolyte, such as a saturated solution of potassium fluoride, by previously dipping it in the latter. It may be found desirable to partially dry out this pad. On top of the pad is laid an electrode 6 which may, for example, be of graphite, or other chemically inert conductor which is connected to the positive terminal 7 of the source 4. Any suitable current regulator 8 may be provided to adjust the density of current taking part in the electrolytic process. I have found 0.2 to 0.5 amperes per square centimeter to be a suitable density. The blank 1 should be kept in contact with the pad only so long as is necessary to affect a reduction of the surface of the layer 2 of the metallic condition.

Referring to the modification of my invention shown in Fig. 2, a copper blank 1, having a layer 2 of oxide formed thereon, is supported on a conductor 9 of any suitable material which is connected to the negative terminal 3 of a source of current 4. Connected to the positive terminal 7 of source 4, is a member 11 which may, for convenience, hereinafter be termed a brush. This member 11 comprises a core 12, which may be of woven asbestos, clamped in a conducting collar 13. The end of the brush 12 remote from the oxide layer may be dipped into a container 14 filled with an electrolyte 15. The member 12 acts as a wick and conductsthe electrolyte l5 downward to its lower end 16, as shown in the drawing. The end 16 may then be rubbed over'the surface of layer 2 until the required reduction has taken place thereon. By this means, the impregnation of the electrolyte into the surface of the layler 2 is prevented. I have found that, with t is method, ahigher current density than that which is usual in electrol tic processes may be employed. For examp e, a density of ten amperes per square centimeter has been found to give satisfactor results. At present, I regard the effect the heat developed at the surface in drying out the electrolyte before it can penetrate the pores of the material, as furnishing a probable explanation of the desirable results obtained. Because of the rectifying action of the junction between the oxidized copper and the mother metal, an alternating electromotive force may be substituted for the direct-current sources above described, if it is desired to do so.

It will be evident that, while I have described this electrolytic process in connection with electrolytic reduction of a surface of oxidized copper, it is broadly applicable to many other electrochemical processes, such as metallic deposition, as will be evident to those skilled in the art. I desire, therefore,

that the following claims be given the broadest interpretation of which they are susceptible in view of their expressed terms and of the prior art.

so I claim as my invention:

1. The method of producing a conductive layer on the surface of an oxidized cop r disc which consists in connecting said isc to one terminal of a source of electric current and placing it in contact with a fibrous ad impregnated with an electrolyte adapte to yield reducing ions when connected to the other terminal of said source.

2. Apparatus including a cathode faced with copper oxide, an absorbent body serving as an anode and impregnated with electrolyte and movable over the face of the copper oxide, the electrolyte being of such a character as to yield hydrogen ions at the copper oxide surface, and electrical supply means for the electrodes.

3. In a method of preparing a conductor having a uni-lateral electric conductivity, the steps of electrolytically reducing the surface of an oxidized layer at such a current density as to vaporize all electrolyte making contact with said layer before it has time to penetrate through said layer.

In testimony whereof, I have hereunto subscribed my name this 21st day of Septemen,

JOSEPH SLEPIAN. 

